Freud's Last Session consists of a doc and a don debating life and death — a matter of no small concern for the actors playing them. The doctor, you've guessed, is Sigmund Freud (Martin Rayner), the ultimate psychoanalyst, now cancer-ridden and on the brink of the Hereafter. The Oxford don is anybody's guess, so playwright Mark St. Germain imagines here he might be C.S. Lewis (Mark H. Dold), the author and academic, shortly after he abandoned Freud's stance of atheism for Christianity.

"You get the impression that one of the reasons for this supposed meeting is that Freud is taking a last look at why someone so intelligent would believe in a god and argue it through so that he [Freud] could, in some ways, perhaps affirm himself and his own beliefs," says the man who speaks for Freud on stage. "I think what's really important about the play is how they bond when they're from opposing views."

The time is Sept. 3, 1939, literally hours after the beginning of World War II — and 20 days before Freud ended his life with an assisted suicide. This is not the way one wants to remember the Father of Psychoanalysis, Rayner notes, "so it's been somewhat sanitized and it's certainly not dwelt upon, but he had an agreement with his doctor that he would take care of him at the end. As I understand it — although there are some mixed messages about this — he was given two doses of morphine when he told his doctor, 'Enough torture. No more torture.'"

This is the sixth coming of Freud's Last Session. It was originally mounted by director Tyler Marchant for 14 performances at Barrington Stage Company's Stage 2 in Pittsfield, MA, but it broke enough house records to warrant three revivals and become the company's longest-running hit. It moved to Off-Broadway in summer 2010. Now, after a 45-day hiatus, it has resumed its New York run at the Marjorie S. Deane Little Theater at the West Side Y, an intimate, underused venue that seamlessly blends in with Freud's London study. [AUDIO-LEFT] Why this groundswell of popularity? Rayner has his theories: "It seems to be a combination of very well-known thinkers and a place where people can hear a discussion of beliefs. Also, it's a discussion full of wit, not dry at all. Word of mouth has been enormous. People come back to see it two or three times because it's like a complicated piece of music that you can listen to again and again. Often they say to me, 'There's nothing in town like this to see,' so we're performing a sort of service."

Interestingly, both actors subscribe in real life to the philosophies of the characters they are playing — making the acting extra easy. Furthermore, this is Rayner's second Freudian session. He did the role 25 years ago in Dallas in something called The Couch, where Freud and C.G. Jung verbally dueled with their ideas.

That prior experience doubtlessly helped, but Rayner nailed the role this time with a cold audition. "Nobody knew me at Barrington. It was one of those things where I auditioned and they thought I was right. When I first read the script, I thought, 'I know who this man is.' From the audition on, I just had a hold of him in some way."

Something else uniquely qualified Rayner for the part: "I was diagnosed four years ago in a fairly advanced state of cancer, but I had really great treatment in Georgia — a seed implant and external radiation, which worked in the sense it killed my prostate stone dead — but, by then, the cancer had spread to my lymph system."

He kept his condition a secret until after the play opened in June. Then, he explained to Dold and others about the unorthodox raw food snacks he takes to strengthen his immune system. His bible is Patrick Quillin's book, "Beating Cancer with Nutrition."

"That's my ticket to where I am today. Within a year of doing what the book says, I improved my PSA score by 75 percent. Although I'm technically incurable, I'm doing incredibly well on this process. I've become very healthy so I have an enormous amount of energy to play roles. Since Freud is so demanding vocally and physically, I am actually in great shape to do it. I'm, right now, about as fit as I have ever been."

The role has fortified the actor. "I just had a very strong instinct about this part. I think it really comes from the fact that most of my career — all of my career, really — has been very much a sort of Alec Guinness process, and that is: I don't really play myself much, I transform a great deal. That seems to be the center of my gift."

It's a gift that has kept him from stardom. Twice, he originated — and triumphed in — roles that went to Broadway with name-brand actors: Judd Hirsch in Sixteen Wounded and a Tony-winning Richard Easton in The Invention of Love. Rayner stayed on as understudy but never went on. Now, at last, he's making his mark in New York with the role of a lifetime, and it couldn't come at a better time.